The present invention generally relates to print heads for printers, and more particularly to a head (or an inkjet head) for use with an inkjet printer. The inkjet head of the present invention is applicable not only to a single printer unit but also widely to copiers, facsimile machines, computer systems word processors, and combination machines thereof which have a printing function.
Among inkjet heads, those which employ a piezoelectric element have increasingly come into the limelight in recent years due to their excellence in energy efficiency. This type of inkjet head typically includes a piezoelectric element, one common ink chamber which receives from an external device and stores ink, a plurality of pressure chambers coupled to the piezoelectric element, and a nozzle plate so connected to the pressure chambers that a nozzle may be connected to each pressure chamber. Each pressure chamber is connected to the common ink chamber through an ink supply channel so that it may receive ink from the common ink chamber and increase its internal pressure using deformation of the piezoelectric elements, thereby jetting ink from each nozzle.
In recent years, piezoelectric elements have often been manufactured by printing or sputtering of LSI technology. The LSI technology facilitates miniature piezoelectric elements, while the miniature ink supply channels are needed as well. A higher resolution is also needed by reducing an interval between two nozzles of adjacent pressure chambers (i.e., nozzle pitch) and increasing the number of nozzles. The miniature ink supply channels are also required for this purpose. The miniature ink supply channels are thus sought for both manufacturing and higher-resolution purposes.
According to ink""s hydraulic resistance equivalence, a doubled number of ink supply channels would make the length of the ink supply channel twice as long as that of one ink supply channel. A quadrupled number of ink supply channels would make the length of the ink supply channel four times as long as that of one ink supply channel. Thus, in terms of hydrodynamics, ink""s hydraulic resistance equivalence is maintained by increasing the length of the ink supply channel by the number of ink supply channels.
On the other hand, an ink supply channel has been demanded which is longer than a distance between adjacent pressure chambers since a long ink supply channel would enhance rigidity and strength of a wall between the common ink chamber and each pressure chamber. Some head configurations are required to be a adhered to a thin film before being adhered to a piezoelectric element in a pressure-chamber plate that includes pressure chambers, ink supply channels and a common ink chamber. Such a head calls for a longer ink supply channel so that the thin film can be firmly adhered to a larger area between each pressure chamber and the common ink chamber.
For these requirements, each pressure chamber has been allocated a plurality of (e.g., four) ink supply channels that align with a direction in which the pressure chambers are arranged in a conventional inkjet head.
However, the instant inventors have discovered those ink supply channels, which align with a direction in which the pressure chambers are arranged as in the conventional inkjet head, would prevent a higher resolution. This is because a nozzle pitch that is designed to be narrow so as to attain a high integration would necessarily lead to the narrow pressure chamber width, and it would be extremely difficult to establish multiple ink supply channels in the narrow width.
Accordingly, it is an exemplified general object of the present invention to provide a novel and useful inkjet head and its manufacturing method in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide an inkjet head and its manufacturing method which may realize a high resolution, maintain at a desired strength a wall that defines an ink supply channel between a common ink chamber and each pressure chamber, and secures a sufficient adhesion area on the wall.
The present invention also has an object to provide an inkjet head and its manufacturing method which allocate a plurality of ink supply channels so as to connect each pressure chamber to the common ink chamber, and use a dry film resist for high-precision and efficient manufacturing.
To achieve the above objects, an inkjet head of the present invention comprises a pressure-chamber plate which includes a plurality of pressure chambers which store ink and a plurality of ink supply channels that supply the pressure chamber with the ink, a piezoelectric element that may pressurize the pressure chamber in the pressure-chamber plate, and a nozzle plate that includes a nozzle which jets the ink in the pressure chamber when the piezoelectric element pressurizes the pressure chamber, wherein some of the ink supply channels are connected by the plural number to each pressure chamber, and arranged in a direction perpendicular to that in which the plurality of pressure chambers are arranged. Alternatively, said ink supply channels may be connected by the plural number to each pressure chamber, and arranged two-dimensionally at random with respect to a plane parallel to a direction in which the plurality of pressure chambers are arranged.
A manufacturing method for an inkjet head which is manufactured by joining a plurality of layered members that is made of independent multiple layers, including the step of forming one of the plurality of layered members which comprises the steps of forming a layered member by laminating a dry film resist onto a substrate having a predetermined shape, exposing part of the layered member which corresponds to pressure chambers, an ink supply channel, and a common ink chamber, and developing the layered member, wherein a plurality of ink supply channels are formed and connecting each of a plurality of pressure chambers to the common ink chamber, a direction in which the plurality of pressure chambers are arranged being perpendicular to that in which the ink supply channels allocated to each of the plurality of pressure chambers are arranged.
A manufacturing method of an inkjet head of the present invention comprises the steps of forming first and second layers defining at least one of an introduction path, a pressure chamber, an ink supply channel and a common ink chamber by using a dry film resist, forming a rigid layer on either one of the first and second layers, and joining the first and second layers to each other via the rigid layer.
A printer of the present invention comprises an inkjet head, and a drive unit which drives the inkjet head, wherein the inkjet head comprises a pressure-chamber plate that includes a plurality of pressure chambers which store ink and a plurality of ink supply channels which supply the pressure chambers with the ink, a piezoelectric element that may pressurize the pressure chamber in the pressure-chamber plate, and a nozzle plate that includes a nozzle which jets the ink in the pressure chambers when the piezoelectric element pressurizes the pressure chamber, wherein part of the ink supply channels are connected to each pressure chamber, and arranged in a direction perpendicular to that in which the plural pressure chambers are arranged.
A printer and an inkjet head of the present invention include a plurality of ink supply channels that are connected to each pressure chamber and arranged in a direction perpendicular to a direction in which the pressure chambers are arranged. Therefore, where the predetermined number of ink supply channels is needed, all of them need not align with a direction in which the pressure chambers are arranged. This however intends to exclude a structure in which all of the ink supply channels align with a direction with which the pressure chambers align, and not to prohibit some of the ink supply channels from aligning with the direction with which the pressure chambers align. For example, given three ink supply channels, two of them may align with a direction with which the pressure chambers align. Alternatively, the ink supply channels may be arranged two-dimensionally at random, independently of the direction in which the pressure chambers are arranged. Hereupon, the clause xe2x80x9carranged two-dimensionally at randomxe2x80x9d intends to exclude a structure in which all of the ink supply channels align only with a direction with which the pressure chambers align, as described in more detail in the following embodiments.
The number of ink supply channels that are allocated to each pressure chamber of the present invention is determined as follows. Firstly, a size of one ink supply channel that may maintain a proper balance with ink""s hydraulic resistance as described in the following embodiment with reference to FIG. 6 is determined in terms of the depth, length and width of the ink supply channel. Where a dry film resist is used to create an ink supply channel, the thickness of the dry film resist becomes the depth of the ink supply channel. Thus, from among some dry film resist candidates having different thickness, those dry film resists having the depth with little fluctuation in terms of the depth, length and width of the ink supply channel are selected. This determines the thickness of a dry film and consequently the size of the ink supply channel. The ink supply channel determined here, however, becomes shorter than an interval (i.e., wall thickness) between the adjacent pressure chambers, and would deteriorate the strength and adhesion with another component of the wall that defines the ink supply channels. The present invention accordingly intends to keep ink""s hydraulic resistance equivalent by setting the ink supply channel to be at least equal to, or preferably longer than, the wall between the pressure chambers, while setting the number of ink supply channels to be a quotient produced by dividing the wall thickness between the pressure chambers by the original length of the ink supply channel.
A member with a high Young""s modulus, if provided between two adjacent ink supply channels connected to each pressure chamber, would prevent these ink supply channels from negatively influencing each other, keeping them stable.
The manufacturing method of an inkjet head of the present invention allows the ink supply channels made of a dry film resist to align with a direction different than that with which the pressure chambers align. A metal or ceramic layer, if provided between two dry film resists that form an ink supply channel, would keep adjacent ink supply channels stable even after they are joined. A resin or composite resin member, if used in place of metal or ceramic, has a thermal expansion coefficient close to that of a dry film resist, and would provide an inkjet head with thermally homogeneous components.
The manufacturing method for an inkjet head of the present invention that provides a layer comprising such a rigid member as metal or ceramic between the adjacent layers defining ink supply channels, may be widely applied in general as a manufacturing method for an inkjet head using dry film resists.
Other objects and further features of the present invention will become readily apparent from the following description of the embodiments with reference to accompanying drawings.
FIG. 1 is a schematic perspective view of an inkjet printer to which an inkjet head of the present invention is applicable.
FIG. 2 is a partial plan view of an inkjet head of a first embodiment according to the present invention.
FIG. 3 is a cross section taken along line A-Axe2x80x2 in FIG. 2.
FIG. 4 is a cross section taken along line B-Bxe2x80x2 in FIG. 3.
FIG. 5 is an exemplified variation of the arrangement of ink supply channels shown in FIG. 4.
FIG. 6 is a graph that shows the relationship among the depth, length and width required for one ink supply channel in order to realize the desired ink hydraulic resistance.
FIG. 7 is a perspective view showing a series of manufacturing steps for an inkjet head of a first embodiment of the invention.
FIG. 8 is a flowchart for explaining the manufacturing steps in FIG. 7.
FIG. 9 is a flowchart for explaining part of the flowchart in FIG. 8 more concretely.
FIG. 10 is another flowchart for explaining part of the flowchart in FIG. 8 more concretely.
FIG. 11 is a partial plan view of an inkjet head of a third embodiment of the present invention.
FIG. 12 is a cross section taken along line A-Axe2x80x2 in FIG. 11.
FIG. 13 is a cross section taken along line B-Bxe2x80x2 in FIG. 12.
FIG. 14 is a partial plan view of an inkjet head of the third embodiment according to the present invention.
FIG. 15 is a cross section taken along line Axe2x80x94A in FIG. 14.
FIG. 16 is a cross section taken along line B-Bxe2x80x2 in FIG. 15.
FIG. 17 is a perspective view showing a series of manufacturing steps for an inkjet head of a third embodiment according to the present invention.
FIG. 18 is a flowchart for explaining the manufacturing steps in FIG. 17.
FIG. 19 is a flowchart for explaining part of the flowchart in FIG. 18 more concretely.
FIG. 20 is another flowchart for explaining part of the flowchart in FIG. 18 more concretely.